FILE - In this Sept. 2, 2019, file photo, provided by the Santa Barbara County Fire Department, firefighters work to extinguish a dive boat engulfed in flames after a deadly fire broke out aboard the commercial scuba diving vessel off the Southern California Coast. The owners of the dive boat where 34 people perished in a fire off the coast of Southern California filed a legal action in federal court Thursday, Sept. 5, 2019, to head off potentially costly lawsuits. Truth Aquatics Inc., which owned the Conception, filed the action in Los Angeles under a pre-Civil War provision of maritime law that allows it to limit its liability. (Santa Barbara County Fire Department via AP, File) less

FILE - In this Sept. 2, 2019, file photo, provided by the Santa Barbara County Fire Department, firefighters work to extinguish a dive boat engulfed in flames after a deadly fire broke out aboard the commercial ... more

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FILE - In this Sept. 2, 2019, file photo, provided by the Santa Barbara County Fire Department, firefighters work to extinguish a dive boat engulfed in flames after a deadly fire broke out aboard the commercial scuba diving vessel off the Southern California Coast. The owners of the dive boat where 34 people perished in a fire off the coast of Southern California filed a legal action in federal court Thursday, Sept. 5, 2019, to head off potentially costly lawsuits. Truth Aquatics Inc., which owned the Conception, filed the action in Los Angeles under a pre-Civil War provision of maritime law that allows it to limit its liability. (Santa Barbara County Fire Department via AP, File) less

FILE - In this Sept. 2, 2019, file photo, provided by the Santa Barbara County Fire Department, firefighters work to extinguish a dive boat engulfed in flames after a deadly fire broke out aboard the commercial ... more

Could the batteries used to power a variety of scuba equipment have contributed to the deadly Conception dive boat fire earlier this month?

No cause has been determined in the blaze that killed 34 people in their sleeping quarters aboard the 75-foot dive boat anchored in Platt’s Harbor roughly 20 nautical miles from Santa Barbara. However, a U.S. Coast Guard bulletin issued Wednesday in response to the tragedy raised more questions about whether lithium-ion batteries may have played a role.

“This bulletin identifies regulations related to firefighting, lifesaving, preparations for emergencies, and means of escape that serve as a reminder for owner and operators to ensure the safety of the passengers and crew while onboard,” the bulletin stated.

The bulletin specifically recommended “limiting the unsupervised charging of lithium-ion batteries.” In diving, many pieces of equipment, such as lights, cameras, computers and modern breathing technology, use such batteries.

The cause of the fire has been a source of discussion not only among divers, but among charter boat operators — especially those who knew the owners and crew at Truth Aquatics, which operated the doomed Conception.

Bob Kennedy, who started a similar company, Catalina Divers Supply, 35 years ago and still runs it today, said the fire “would have to be catastrophic — something that didn’t give the crew time to respond.” He said that all but rules out a kitchen fire or even a fire in the engine room, which is equipped with an extinguishing system. And diesel fuel, he said, isn’t flammable.

However, “we’re all aware of lithium-battery-related fires,” he said. “Airlines won’t let you travel with scooters or pack lithium batteries.”

It turns out that divers typically bring plenty of lithium-charged products on dive boats, which these days have charging stations to keep them juiced, Kennedy said. Such products include underwater diving propulsion vehicles — known as scooters — that push divers along so they don’t have to kick. There are also underwater canister lights.

“Was one of those on board and being charged? Could it have been a scooter?” Kennedy said. “I imagine it wasn’t a GoPro,” which he said would have been too small.

“The whole thing’s spooky,” Kennedy said. “There are a lot of charter boats out there that are not as well-staffed and well-maintained (as Truth Aquatics’). If it could happen aboard that boat, it could happen to anybody. It’s scary.”

Last week, NTSB member Jennifer Homendy said the Conception’s galley housed a kitchen with an electric stove as well as “a lot of wiring and electrical systems” throughout. She added that there may have also been videography and photography gear charging overnight.

The cause of the blaze is under investigation, but Homendy said authorities are “not ruling out any possible ignition sources,” such as the electrical system.

The Coast Guard bulletin also included ensuring that crew members know what to do in an emergency and that escape routes are clearly marked, training and maintenance records are up to date, firefighting and lifesaving equipment are working and on board, and passenger areas are free of hazardous arrangements.

Five crew members survived the Sept. 2 fire. On Wednesday, officials said they recovered the remains of the last missing passenger from the underwater debris field.